Action Points

Low back pain arising from ergonomic and occupational exposures is an important cause of disability particularly in the agricultural sector and in developing countries.

Low back pain is on the rise and causes more global disability than any other condition, according to two studies from Australia.

The number of disability-adjusted life years (DALYS) due to low back pain increased from 58.2 million (95% CI 39.9 million-78.1 million) in 1990 to 83 million (95% CI 56.6 million-111.9 million) in 2010, wrote Damian Hoy, PhD, of the University of Queensland, and colleagues in the Annals of the Rheumatic Disease.

"The global point prevalence of [low back pain] was 9.4% (95% CI 9.0-9.8)," they said.

Prevalence was higher in men (mean 10.1%, 95% CI 9.4%-10.7%) compared with women (mean 8.7%, 95% CI 8.2%-9.3%). Both prevalence and burden of disease increased with age, with peak prevalence "at around 80 years of age," the authors wrote.

In a second study appearing in the same issue of the journal, other researchers looked specifically at the global burden of low back pain as a result of exposure to occupational ergonomic risk factors. They estimated that worldwide ergonomic work exposures were responsible for 21.7 million DALYS in 2010.

"Bottom line -- the human cost globally is much higher than previously estimated," James McDeavitt, MD, chair of physical medicine and rehabilitation at Baylor College of Medicine in Houston, told MedPage Today.

High Worldwide Prevalence

The analysis by Hoy's group was part of the Global Burden of Disease (GBD) 2010 study. Out of 291 conditions evaluated, low back pain ranked highest in terms of years lived with disability and sixth in DALYS, the authors said.

They reviewed 117 studies and 780 estimates of burden of disease for low back pain, including data from 85 countries, and 20 of 21 world regions covered by the GBD study. The majority of studies used in the analysis included both men and women, a broad age range, and urban and rural populations.

In the GBD 2010 study, low back pain was deﬁned as "pain in the area on the posterior aspect of the body from the lower margin of the 12th ribs to the lower gluteal folds with or without pain referred into one or both lower limbs that lasts for at least 1 day."

Four levels of severity were identified for low back pain, each with their own disability weights. The disability weights were applied to the prevalence values to derive the overall disability of low back pain expressed as years lived with disability.

"The results show that the prevalence and burden of low back pain is very high throughout the world," Hoy's group wrote, adding that because low back pain appears to peak in older age groups, the burden of low back pain ranked higher in regions with longer life expectancies, they said.

In 2010, the age-standardized prevalence was highest in western Europe (mean 15%, 95% CI 14.1-16.0) followed by North Africa/Middle East (mean 14.8%, 95% CI 13.8-15.9).

Prevalence did not change signiﬁcantly from 1990 to 2010, the authors stated.

The study had some limitations. The GBD study of low back pain referred to body function and structure, but did not refer to "broader aspects of life such as participation, well-being, career burden, and economic impact," Hoy's group wrote.

Going forward, "it's important that burden of disease estimates are supplemented with this information to consider the full impact of a condition in a population," they said.

What's more, there was "considerable methodological variation" between studies used in the analysis. The analysis also included the Medical Expenditure Panel Survey (MEPS), the authors said, which might have contained some recall bias, and may not be representative of experiences across the globe.

They called for further research on the duration, severity, and disability over the course of low back pain.

"With expanding and aging populations in many low-income and middle-income countries, the enormous burden from low back pain in these areas will grow significantly over coming decades," they said.

McDeavitt called the current study an improvement over the 1990 GBD and its 2000-2004 follow-up. In the former, the condition was not even reported as an issue because it was not included in the analysis, he said.

In the 2000-2004 update, back pain was reported to rank 105 out of 136 disabling conditions. But "the study was flawed in that it used a definition of spine disease that was highly dependent upon high-tech imaging. Many countries in the study group would not be expected to use imaging to the extent used in developing countries," he said.

The current study attempted to address these methodological challenges, he added.

Ergonomic Exposure

In the second study, Tim Driscoll, PhD, of the University of Sydney, and colleagues, reported that occupational exposure was a substantial contributor to all low back pain, accounting for 28% of all DALYS from low back pain for people, ages 15 and up. The highest relative risk (3.7) was in jobs in the agricultural sector.

They found that 62% of low back pain DALYS were in men, with the largest numbers occurring in those between the ages of 35 and 55. Specifically, of the 21.7 million DALYS in 2010, 13.5 million were in males and 8.3 million in females.

Exposure prevalence was based on occupational distribution, the authors said. Estimates of relative risk were based on a meta-analysis of published literature.

The largest number of DALYS due to work exposure occurred in East Asia and South Asia, "but on a per capita basis the biggest burden was in Oceania," they said.

The absolute burden increased "considerably" from 1990 to 2010, in line with population increases and an aging population, the authors said, "but decreased an average of 14% when calculated on a per capita basis."

The results "provide strong support" for the need to identify, develop, and implement effective interventions that minimize exposure to ergonomic risk factors.

Known risk factors for occupational conditions that lead to low back pain are rapid pace of work, repetitive motion, insufficient recovery time, vibration, heavy lifting, bending, twisting, and sustained non-neutral postures, they explained.

But they cautioned that, when considering interventions, the relationship between various risk factors and low back pain incidence may not be straightforward. Many current interventions are not supported by strong evidence, especially training and administrative measures, they said.

With regard to study limitations, occupation was used as a proxy for exposure to work-related ergonomic factors.

"Ideally, measures of the exposures themselves would be available," the authors said.

In addition, the relative risk for the population attributable fraction was based on a meta-analysis of studies that used "somewhat" different methodologies, and most of the studies used in calculating relative risk were based in developed countries, but were applied to all.

Nonetheless, "what this says is that low back pain is a real problem in this country and others," said Richard Simpson Jr., MD, PhD, a neurosurgeon at Houston Methodist Hospital. "What's needed is a way to get people back to work asap."

Simpson said that getting some people back to work might go beyond preventive measures. Patients who are already incapacitated need to be educated about what resources and strategies are available to them to help them return to the workplace. Some might even require surgery and/or implantable devices if conservative care fails, he said.

The study by Hoy's group was funded by the Bill and Melinda Gates Foundation, the Australian Commonwealth Department of Health and Aging, the Australian National Health and Medical Research Council, and the Aging and Alzheimer's Research Foundation. The authors reported no conflicts of interest.

Driscoll was supported in part by funding from the National Occupational Health and Safety Commission (now Safework Australia). The authors reported no conflicts of interest.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania

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